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Fish tank pump == Vaccume pump

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LAN_403

Killa-X

Thu Oct 14 2010, 03:19AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Awhile ago I picked up one of these units at target, on sale, for $5. I used it for a long awhile with experiments, as I believe its rated 1-2 PSI. After tinkering around, i manage to make it into a vacuum pump. I had to apply hot glue to the sides, the feed, and the screw, to 100% seal it. Then I drilled a hole in the shell, and added a tube. I was able to pull a vacuum onto a pop bottle, enough to squeeze it in.

The main reason for this project, was so when I oil-dunk my 4 MOTS, I could vacuum seal it, and remove the air after adding the oil. I think this will have enough pumping power to do the job. Maybe not instantly, but over time.

I thought I'd just share a method to make a simple cheap vacuum!

Simple. Easy. Effective.

Arcstarter

Thu Oct 14 2010, 03:34AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I'm not so confident it will be able to pull a hard enough vacuum to suck the air bubbles out. A fridge or A/C compressor would do, but one of those would make a water bottle look like it would if under a truck's wheels.

Killa-X

Thu Oct 14 2010, 03:46AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Arcstarter wrote ...

I'm not so confident it will be able to pull a hard enough vacuum to suck the air bubbles out. A fridge or A/C compressor would do, but one of those would make a water bottle look like it would if under a truck's wheels.

Yeah I see your point. Some use 12v tire compressors by adding a tube to the intake side of the pump. I'm sure a small scale test can be formed. Glass jar, oil, and some object that will be able to trap air, which gets removed by the pump. I can try some stuff tomorrow, unless there's anything else you'd like to see my put this to. Open for suggestions seeing in the only one with one probably :D

IntraWinding

Thu Oct 14 2010, 12:30PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

How about this as a test:

Put an inverted test tube in your vacuum chamber. Add enough oil to the chamber to cover the test tubes open mouth plus extra (at least one test tube full). Now pump the chamber down as far as you can (indicated when no more bubbles escape from the test tube mouth). now bring the vacuum chamber back to atmospheric pressure at a controlled rate so that oil is drawn up into the test tube. Note the size of the bubble remaining in the tube when you reach atmospheric pressure. The reduction from a full tube of air to the remaining bubble indicates the effectiveness of your pump with a transformer. You might want to degas the oil under your vacuum for some while before doing the test in case the oil contains any volatiles.

Killa-X

Fri Oct 15 2010, 12:38AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Results...

Started with a glass jar. sealed, and a plastic vile. Had no liquid in the mouth side, just air all the way to the mouth. Once i formed the vacuum until no bubbles accrued for 10 minutes, I released it, and it sucked up 3 lines.

Means, it went up 22mms. the vile is 14mm ID...and 125mm long. Really cruddy i guess. Even a plastic bag to the hose, makes a dimple, but doesn't even have the pressure to 'pop' it. Oh well, was worth a try! It still vacuums, just not a lot. I guess my next cheapest bet is the famous "Hack a car tire pump"

IntraWinding

Fri Oct 15 2010, 01:01AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Oh well, at least you can measure what you've got now.

I wonder how much air would be left if you tried that test with a good two stage rotary vacuum pump? I reckon it would be close to nothing.

At very low pressures though the oil will will trap some air in the test tube and so give a misleading result. It would be better to stick a magnet on the test tube so you can hold it above the liquid surface with another magnet outside the jar until you finish pumping and then lower the tube back into the liquid before letting the air back into your jar.

Don't forget to look out for a dumped fridge you can take the compressor from. Some people get good results from these (mine wasn't one of them).

Two pumps in series are likely to be better than one.

Killa-X

Fri Oct 15 2010, 01:13AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Yup. I hear people use 2-4 of these for pumping air faster. The type is the issue.

These pumps are vibrators. It's like the 'pump button' on a snowblower. A little rubber dome that you push down to pump air. A magnet is placed in front of half an E-Core. It moves left/right at 60hz. This left/right movement forces an arm to move...Causing it to pull/push on the pumping 'button'

So you can tell it wouldn't be that powerful. It's just magnetic fields. Especially because it's so low of a current. I think it did good, for the type of pump it is.

I just saw on instructables long ago, you can hack a car pump to suck a good amount of force.

IntraWinding

Fri Oct 15 2010, 01:12PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Yes, diaphragm pumps benefit from strings of up to four in products I've seen but still don't get as low as oil sealed rotary vacuum pumps which appear to hit the lower practical vacuum limit for 'positive displacement' pumps with just two stages.

A good water powered 'Venturi Pump'/'Filter Pump'/Aspirator can get down to the vapour pressure of the water (a few Torr), which is way better than that modified tyre pump. One idea I had was to use one with oil and a pump in a closed loop, but the pump would probably cost as much as a rotary vacuum pump...

A second hand vacuum pump intended for repairing fridges and air conditioners is one way to go.

I got a two stage rotary vacuum pump off eBay quite cheap, but it was badly rust pitted internally. I learnt a lot stripping it down and managed to repair it with high temperature epoxy resin.

What will you try next?

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